The primary objective of this case-control study is to explore the postulated association between CLL and chronic antigenic stimulation related to infectious, inflammatory processes and autoimmune diseases by means of medical chart review and interview. We are studying the possible association of CLL with occupation, smoking, alcohol use, immunizations, and operative procedures involving the lymphoproliferative system for the purpose of developing additional etiologic hypotheses. Cases are ascertained both retrospectively (July 1, 1969 through December 31, 1979) and concurrently (January 1, 1980 through December 31, 1982). Hospital record room searches of eight Baltimore SMSA hospitals and 18 physicians' offices have yielded 355 cases of CLL. An additional 25 concurrent cases have been identified through physicians' offices. Each case is matched with two controls with any malignancy other than a lymphoproliferative neoplasm and two controls with any non-malignant disease. The matching variables include age (within five years), sex, race, date of diagnostic admission (within six months) and hospital of admission. For the concurrent study, the non-cancer controls are being obtained through random digit dialing. All living cases are interviewed in person and HLA blood drawn. We hope to identify differences of HLA types between patients with CLL and controls and to correlate these differences with epidemiologic and clinical characteristics of various subgroups of cases and controls. The postulated increased familial incidence of CLL and other lymphoproliferative malignancies will be explored. Families with histories of two or more first degree relatives with CLL or other lymphoproliferative malignancies will be studied by interviewing siblings and children of index cases.